Extendable and Retractable Tennis Racquet

ABSTRACT

One embodiment of an extendable and retractable tennis racquet contains a stringed area  01,  throat  02,  and shank  03  as one integral member. The handle is comprised of a shank inside of a hollow handle  05.  A spring or flexible means  07  connects the shank to the hollow handle. When the racquet is swung, the centrifugal force generated pulls on the head assembly. The shank slides outward telescopically, thereby increasing the length of the racquet. At the end of the racquet swing, the restoring force of the spring overcomes the diminishing centrifugal force, which pulls the shank back to its retracted position. Other embodiments are described and shown.

BACKGROUND 1. Field of Invention

This invention relates to tennis racquets, and more particularly, to tennis racquets having a mechanism to change its length during gameplay.

2. Discussion of the Prior Art

Many adjustable length racquets have been proposed in the past. Despite having some of the same common goals, the applications are significantly different. One main area of focus was the interchangeability of the racquet. Many previous inventions tried to address a means to exchange a handle or a portion of the handle in order to suit the individual needs of a particular player. Another area of focus was a means to adjust the racquet length using either common, everyday tools or specific tools. Very few prior art inventions allowed for a quick adjustment that could be achieved during gameplay.

In U.S. Pat. No. 4,746,119 to Jeanrot dated May 24, 1988, a retractable racquet is shown in FIG. 4. The purpose of retraction is to provide an easier mode of transportation for the racquet. This racquet is not meant to be changed during gameplay.

Many of the past inventions were focused on providing an adjustable length racquet. Many of the noted efforts include U.S. Pat. No. 5,169,145 to Jang, U.S. Pat. No. 4,641,838 to Gabrielidis, U.S. Pat. No. 4,671,511 to Trysinksy, U.S. Pat. No. 6,030,302 to Chojnacki, U.S. Pat. No. 6,033,325 to Hong, U.S. Pat. No. 4,545,584 and 4,691,926 to Adam, and U.S. Pat. No. 3,833,219 to Dean. All of these prior art inventions have a way to adjust the racquet length by means of grooved sockets, pins, screws, or bolts. However, none of these means can be used to quickly change the length of the racquet. Tools are often required to make the necessary adjustments. Another drawback to these inventions is that with the racquet extended, many players would hit the ground with the racquet on the take-back during the serve.

A rapidly adjustable racquet is shown in U.S. Pat. No. 3,931,968 to Hedberg dated Jan. 13, 1976. This invention requires the player to use both hands in order to slide the shank to the preferred length. The racquet remains at the specified length as long as the grip is held tightly. It also requires the player to decide when and to what degree to extend the racquet. This takes away focus from the game and distracts the player. Lastly, it would be very challenging to use this invention on the serve because the player would have to make the adjustment mid-swing. If the adjustment was made at the onset of the swing, the extended racquet would hit the ground on the takeback.

In yet another known prior art, U.S. Pat. No. 5,524,879 to Lyle dated Jun. 11, 1996, a locking sleeve is used in conjunction with a spring loaded roller to easily adjust the length of a racquet. This invention also requires both hands to operate, thus making it a distraction to the player. This mechanism is also not suitable to be used during a serve because of the propensity to hit the ground.

The last prior art worth mentioning is Chinese Pat. CN 205084346 U, to Wang et al. dated Mar. 16, 2016. The invention refers to a telescopic badminton racket. With this barrel cam design, the invention is comprised of radial and longitudinal grooves, detents, and a provision. More specifically, the outer handle has multiple radial grooves and a single longitudinal groove on the inside wall. Detents are embedded at various locations in the radial grooves. The shaft also has a provision at its base to accept a detent to lock it in place. To extend, the shaft must first be rotated along a radial groove and disengaged from its detent. After this, the shaft must be pulled out telescopically along the longitudinal groove and rotated into a different radial groove until another detent is engaged. Apart from the same two drawbacks prevalent in both Hedberg and Lyle, it is questionable whether this arrangement in the badminton racket can be adopted into a tennis racquet. The latter will require a substantial stiffening of the mechanism and a major resizing. These changes are crucial because the tennis ball and the hitting forces are greatly increased from those of badminton.

Objects and Advantages

It is a principal object of the invention to provide a new extendable and retractable tennis racquet which overcomes the disadvantages of the prior art in a simple but effective manner. This biomechanically designed tennis racquet requires no conscious decision from the player or physical adjustment on the racquet. The extension and retraction of the racquet are both done automatically, as a byproduct of the natural swing. This eliminates the distractions that were required in all previous adjustable length racquets.

It is a major object of the invention to afford a height advantage during the serve. The inherent delayed deployment of the mechanism allows the racquet to be swung through the take-back without hitting the ground.

It is another object of the invention to provide an extendable and retractable tennis racquet which affords a longer reach on groundstrokes.

It is yet another object of the invention to provide a more compact racquet configuration at the onset of the swing, resulting in a shortened duration for the complete swing motion. The racquet will accelerate faster due to the decreased drag, similar to a shorter racquet; this translates to a time advantage for the player to move the racquet or to get it into position for the next shot.

It is a further object of the invention to provide a racquet with a varying weight distribution or balance during gameplay. At the start of a swing or a volley, the racquet is at the retracted and compact position. These handling characteristics are comparable to a head-light racquet. When the ball is struck during a serve or a groundstroke, the racquet is fully extended; thus, its handling characteristics are similar to a head-heavy racquet.

It is an additional object of the invention to provide an extendable and retractable tennis racquet which is comparable in weight to a standard racquet. No significant weight penalty is incurred due to its simplistic design.

Accordingly, several advantages of our invention are:

a) The racquet mechanism is based on biomechanics, meaning that the advantages derived from the racquet come as a result of the forces created during the natural movement of playing tennis. As a result, the player does not have to play differently in order to utilize the advantages afforded by our invention. The player can stay more focused on gameplay because the extension and retraction are done automatically.

b) The extendable racquet offers a height advantage during the serve. The contact point of a player with an additional height advantage is higher up from the ground. Thus, the player can hit the ball more downwards. The serviceable area, or maximum area the player can hit into on the serve as a result of his or her vertical reach, is also significantly increased, which allows for a larger margin of error on the serve.

c) On the serve, the inherent delayed deployment of the mechanism allows the racquet to be swung through the take-back without hitting the ground.

d) On the serve and groundstrokes, the racquet is extended at contact. It affords the player a larger moment arm and therefore, better leverage. Thus, the player can hit the ball harder with more spin. The extended racquet also gives the player a longer reach.

e) For two of the three parts of the swing, the invention will afford a time advantage for the player. The retracted racquet at the onset of the swing will accelerate faster due to the decreased drag, similar to that of a compact racquet. This also applies at the end of the swing. The invention decreases the overall duration of any typical shot, giving the player more time to prepare for the next shot.

f) The invention has a varying balance during gameplay. The retracted racquet has the advantages of a head-light racquet: increased control, maneuverability and less shock on the arm. These characteristics are most beneficial during volleys at the net. On the other hand, the extended racquet has the advantages of a head-heavy racquet: increased power and the ability to swing the racquet faster. These characteristics are most beneficial during a groundstroke or on the serve. The extendable and retractable racquet combines all of the aforementioned virtues.

g) Since the racquet mechanism is simplistic in design with few added elements, the increase in weight over a standard racquet is minimal. No specific change in terms of technique is needed to take advantage of the current invention. Therefore, it would be a smooth and easy transition for any player to adopt this new racquet.

Further objects and advantages of our invention will become apparent from a consideration of the drawings and ensuing description.

DRAWING FIGURES

For a better understanding of the present invention, reference is made to the accompanying drawings in which

FIG. 1A depicts a standard tennis racquet.

FIG. 1B shows a sectional view of the preferred embodiment of the present invention with the shank shown in the nominal retracted position.

FIG. 1C shows a sectional view of the preferred embodiment of the present invention with the shank shown in the extended position.

FIG. 2 shows various stages of the serve motion with specific identification of each stage.

FIG. 3 shows a perspective view of the present invention being deployed during various shots.

FIG. 4A shows a perspective view of a tennis court with the shaded area representing the serviceable area with a linear flat serve.

FIG. 4B shows a perspective view of a tennis court with a larger serviceable area due to additional vertical reach.

FIG. 5A shows a sectional view of a second embodiment of the present invention with a mechanical stop feature.

FIG. 5B shows a sectional view of a second embodiment of the present invention with the mechanical stop feature engaged.

FIG. 6 shows a sectional view of a third embodiment of the present invention with a torsion spring, pinion gear, and rack gear.

REFERENCE NUMERALS IN DRAWINGS

01 Stringed frame head

02 Throat 03 Shank 04 Handle

05 Hollow handle 06 Retracted shank

07 Spring

08 Extended shank 09 Stretched spring 11 Start of serve motion

12 Take-back

13 Trophy position 14 Back-scratch position 15 Contact point

16 Follow-through

17 Back swing 18 Forward swing 19 Locus of racquet tip

21 Serve

22 Forehand groundstroke 23 Forehand volley 24 Extended racquet head position 25 Standard racquet head position 26 Additional reach 27 Retracted racquet head position 28 Forward racquet motion 31 Flat serve down the middle 32 Angled flat serve 33 Serviceable area 34 Vertical reach 35 Larger serviceable area due to additional vertical reach 41 Mechanical stop feature on shank 42 Mechanical stop feature on handle 51 Torsion spring 52 Pinion gear 53 Rack gear

Summary

The present invention relates to the field of tennis, especially extendable and retractable tennis racquets. In its broadest aspect, the invention is an extendable and retractable tennis racquet that provides added advantages to players. The racquet design is biomechanical, meaning that the advantages derived from the racquet come as a result of the natural movements of playing tennis. The centrifugal force generated by the natural swing pulls on the head assembly, which extends the racquet. Towards the end of the swing, the player decelerates the racquet, resulting in a diminishing of centrifugal force. As the centrifugal force is overcome by the restoring force in the spring, the head assembly is pulled back to its retracted position. The aforementioned invention described is only one embodiment.

Description of the Preferred Embodiment

Referring now to FIG. 1A, a tennis racquet is shown to comprise of a stringed frame head 01, throat 02, shank 03, and handle 04. The stringed frame head, the throat and the shank together make up the head assembly. For the present invention, as shown in FIG. 1B, the hollow handle 05 is open at one end; part of the retracted shank 06 is positioned inside the cavity of the hollow handle. The shank and the hollow handle are fitted together telescopically, only allowing relative movement in the longitudinal direction. A spring or flexible member 07 connects the base of the shank to the base of the hollow handle. In this nominal position, the shank is retracted far inside the hollow handle. The spring is also in a free state, neither in tension nor compression. FIG. 1C shows an extended positon 08 where the shank is displaced out of the handle cavity, while the spring is being stretched 09.

FIG. 2 shows the various stages of a typical serve motion. At the start 11, the player holds the ball in one hand and racquet in the other. Next, the player takes the racquet back as the ball is tossed upward in the take-back 12. After the ball is tossed, the racquet arm swings backward 17 and then up above the head. This brings the player into the trophy-position 13. Immediately after, the racquet is dropped behind the head into the back-scratch position 14 where the forward swing 18 begins. The tossed ball is struck at the contact point 15 with the arm fully extended. After impact, the racquet decelerates throughout the follow-through 16.

FIG. 3 shows a schematic display of the advantage of the present invention. For the serve motion 21, the ball is struck during the forward swing 18. At the extended position 24, the racquet has a longer vertical reach 26 than a standard racquet 25. For the forehand groundstroke 22, the ball is also struck during the forward swing. The extended racquet has a longer reach than a normal racquet. For the forehand volley 23, the correct technique calls for a short forward motion 28 of the forearm and the racquet. At impact, the racquet remains in the retracted position 27. These principles also apply to the backhand groundstroke and backhand volley.

FIG. 4A shows the prospective view of a flat serve into the opposite service box. The player can serve down the middle of the court 31, angled diagonally across 32, or anywhere in between. The size of this serviceable area 33 by a flat serve is defined by the player's vertical reach 34.

FIG. 4B shows the same prospective view of a flat serve into the opposite service box. An additional vertical reach 26 affords a larger serviceable area 35.

Operation of Invention

The racquet design of the present invention is biomechanical, meaning that the advantages derived from the racquet come as a result of the natural movements of playing tennis. The spring mechanism to extend the racquet is actuated by the centrifugal force generated during the swing. Extension of the racquet allows for longer reach, resulting in more powerful shots. After the ball is struck, the swing motion during the follow-through moderates and the deployment force diminishes. Consequently, the restoring force in the spring retracts the racquet back to its nominal length. Thus, racquet extension and retraction automatically becomes part of the swing. This synchronization does not require conscious decision or physical adjustment, resulting in minimal change for a player to adopt this new racquet. Due to the simplistic design, the weight of the extendable and retractable racquet is comparable to that of a standard tennis racquet.

There is minimum clearance between the shank 03 and hollow handle 05 so that the shank can slide longitudinally in and out of the cavity of the hollow handle without any lateral free play. This tight fit must be maintained throughout the telescopic deployment range to ensure the overall racquet stiffness necessary to hit the ball effectively. Detailed design of both the shank and hollow handle can include complex structural cross-sections to increase the cross-sectional area and moment of inertia, and a mating feature to ensure a tight fit between the parts.

Unlike multiple prior art inventions, racquet deployment does not affect the exterior surface of the hollow handle 05. As such, the removal or reapplication of the grip material is unnecessary. Thus, the grip material can remain on the exterior surface of the hollow handle throughout the racquet extension and retraction.

In the first embodiment of the present invention, FIG. 1B, the spring 07 is in a free state when the shank is retracted 06. During a serve or a groundstroke, the player swings the racquet, imparting motion on the racquet. In doing so, the centrifugal force generated pulls the weight of the racquet head assembly outward, therefore stretching the spring 09 and extending the shank 08 out of the cavity of the hollow handle 05, as shown in FIG. 1C. Towards the end of swing motion, the racquet decelerates. The corresponding centrifugal force is reduced and overcome by the restoring spring force. As a result, the shank retracts back into the cavity of the hollow handle. The advantage is a total lack of conscious decision or physical action required from the player. It is well known that conscious decision-making requires cognitive resources. Increasingly complex decisions place more strain on these resources, so the quality of decision declines as the complexity of decisions increases. This present invention removes conscious decision-making and preserves cognitive resources for gameplay.

On the serve motion, a longer or extended racquet will increase the vertical reach of the player. Refer to the serve motion 21 and additional vertical reach 26 in FIG. 3. The greater reach will equate to the advantage of a taller player. For a flat serve, which tennis players typically use as a first serve, success depends on speed and placement. The latter is a function of the serviceable area within the service box. A taller player has the distinct advantage of accessing a larger serviceable area due to a higher vertical contact point. This is shown in FIG. 4A where the serviceable area 33 is highlighted. With additional reach, the serviceable area 35 is shown to be increased in FIG. 4B. The larger serviceable area allows for a larger margin of error on serve. The extended racquet will also provide a longer moment arm between the gripping hand and the center of the stringed frame head where the ball is struck. This longer moment arm will result in a more powerful shot. Furthermore, the additional vertical reach will allow the player to hit the serve in a more downward manner.

In reality, there is a limitation on the racquet length as can be seen in FIG. 2. In the early part of the serve motion, the player takes back 12 his racquet in the form of a back swing 17. The tip of the racquet clears the ground only by a small margin. The locus of the racquet tip is displayed as item 19. As the racquet lengthens, the propensity for the racquet tip to hit the ground during this part of the serve motion is greatly increased. The present invention alleviates this concern since the slower backward motion does not deploy the racquet mechanism that extends the racquet. It is only during the latter stages of the serve motion that the forward swing 18 develops enough centrifugal force to extend the racquet. This inherent delayed deployment is key to allow for more vertical reach and to prevent the racquet from hitting the ground as well.

The advantages of this invention can be seen in various shots of the game in FIG. 3. During a groundstroke, a longer racquet will afford the advantages of a longer reach 26 during a groundstroke 22. In addition, the longer reach can also generate more force on the ball than that of a standard racquet. This higher force directly translates into a more powerful shot. The player can also hit the ball harder with more spin. While the groundstroke 22 in FIG. 3 shows a forehand shot, the same advantage can be gained in a similar manner for the backhand.

For volleys, the best racquet position is the retracted position where control is of prime importance. The present invention allows the player to maintain the retracted racquet position. In a typical volley shot, there are no large swing motions. Instead, the racquet is moved forward 28 slightly, shown in volley play 23 in FIG. 3. This translation of the racquet does not induce any centrifugal force to deploy the racquet mechanism to extend. Thus, the racquet remains in the preferred retracted nominal position providing better control.

This invention combines the advantages of a head-light racquet and the advantages of a head-heavy racquet in one racquet. The head-light characteristics of increased control, maneuverability, and less arm shock are most beneficial during volleys. On the other hand, the head-heavy characteristics of increased power and faster racquet acceleration are most beneficial during a serve or groundstroke. The invention allows the player to achieve all virtues without having to play differently. The player will have all the advantages based on which shot he or she hits.

In addition to more vertical reach on serves, longer reach on groundstrokes, and the removal of unnecessary conscious decisions, this invention can also generate a time advantage by reducing the overall duration of a serve or groundstroke. At the start of a swing, the racquet is in the retracted position. This more compact racquet configuration will accelerate faster due to the decreased drag, which consequently shortens the duration for the starting portion of the swing motion. In the next part of the swing, the racquet is now fully extended prior to contact. The drag on the racquet is comparable to that of a longer racquet. There are no time advantages to be gained during this small part of the entire swing. In the last part of the swing, the racquet is retracting due to the diminishing centrifugal force. Once again, there will be a time advantage due to the more compact racquet configuration. The overall duration is reduced, giving the player more time to prepare for the next shot.

Since the amount of extension is related to the centrifugal force derived by the racquet on a swing, a player can select the amount of desired extension by choosing a spring with a specific stiffness. In other words, this invention can be customized to the particular preference of the player.

Description and Operation of Alternate Embodiments

FIG. 5A shows the second embodiment of the present invention. The difference between the preferred embodiment and this alternate embodiment is the presence of a mechanical stop. The mechanical stop feature, 41 and 42, is located on the outside of the retracted shank 06 and inside of hollow handle 05 respectively. In the nominal retracted racquet position, the spring 07 is in a free state, and the mechanical stop feature is not engaged.

FIG. 5B shows the same alternate embodiment when the racquet is extended. Similar to the preferred embodiment, the extension of the racquet is actuated by the swing motion. In this case, the spring 09 is stretched and the racquet is extended until the mechanical stop feature, 41 and 42, is engaged. The amount of extension is fixed and pre-determined by the placement of the mechanical stop feature. Any extension force that pulls on the shank 08 will stretch the spring 09 until it has been reacted out at the mechanical stop feature. Therefore, any swing motion will consistently produce the same amount of racquet extension. In practical terms, a player can decide how much racquet extension would be needed to enhance his or her game. A spring of specific stiffness can be installed in the racquet with the mechanical stop feature placed at a specific location. Thus, a normal swing could always produce the same amount of extension.

FIG. 6 shows the third embodiment of the present invention. The retracted shank 06 is connected to the hollow handle 05 via a torsion spring 51, a pinion gear 52, and a rack gear 53. The torsion spring is attached to the pinion gear at one end and the hollow handle at the other end. The pinion gear is attached independently to the inside of the hollow handle. The rack gear is attached to the shank. The pinion gear teeth are engaged to the opposite teeth in the rack gear. During a swing, the centrifugal force generated pulls on the racquet head assembly thus, pulling the retracted shank out of the hollow handle. The rack gear turns against the pinion gear and winds up the torsion spring. Towards the end of gameplay, the swing motion slows and the corresponding centrifugal force diminishes. As the restoring force in the torsion spring overcomes the centrifugal force, the torsion spring unwinds, turning the rack gear in the opposite direction to drive the shank back inward. As a result, the shank is retracted back into the hollow handle. The rack gear design includes a built-in mechanical stop. As the pinion gear rotates, its teeth continue to engage opposite teeth in the rack gear. This dynamic engagement stops when the pinion teeth run into the end of the toothed portion of the rack gear. The pinion gear can no longer turn thus, stopping any more displacement of the shank. Therefore, a mechanical stop is already built into the rack and pinion arrangement.

Conclusion, Ramifications, and Scope

This invention relates to an extendable and retractable tennis racquet that can be used to optimize gameplay on the court. The biomechanical design frees the player from having to make a conscious decision of whether to extend the racket. The longer reach results in a lengthened moment arm and therefore, a more powerful shot.

The spring mechanism used in the current invention can be replaced with a two-way ratchet mechanism with an enabling toggle mechanism and a return mechanism. Once the toggle mechanism is set in place, the racquet can be extended during gameplay. A different setting on the toggle mechanism will enable the return mechanism to retract the racquet to its original length. While this design is still biomechanical in nature, it does require some physical adjustments on the player's part. In addition, the higher complexity of the design will require more elements and may warrant an increase in weight.

As much as this invention was specifically described for tennis gameplay, it can be applied to a variety of racquet sports. An extendable and retractable racquet may be beneficial in squash and badminton. The more compact and retracted position on the racquet will allow for a faster swing and head-light characteristics. This invention is equally advantageous to the golf game. An extendable and retractable shaft will also allow a faster swing and a more powerful drive.

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments. It will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

We claim:
 1. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; and a spring or flexible means to connect both said shank and said handle to prevent said shank to detach from said handle longitudinally.
 2. The tennis racquet of claim 1, wherein said stringed frame head, throat and shank are one integral member.
 3. The tennis racquet of claim 1, wherein said shank and said handle are comprised of complex cross-sections to increase stiffness.
 4. The tennis racquet of claim 1, wherein said handle has a cavity means to accept a portion of said shank.
 5. The tennis racquet of claim 4, wherein said spring or flexible means connects to the inside bottom of the cavity of said handle and base of said shank.
 6. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; a spring or flexible means to connect both said shank and said handle to prevent said shank to detach from said handle longitudinally; and a mechanical stop means between the said shank and said handle.
 7. The tennis racquet of claim 6, wherein said stringed frame head, throat and shank are one integral member.
 8. The tennis racquet of claim 6, wherein said shank and said handle are comprised of complex cross-sections to increase stiffness.
 9. The tennis racquet of claim 6, wherein said handle has a cavity means to accept a portion of said shank.
 10. The tennis racquet of claim 9, wherein said spring or flexible means connects to the inside bottom of the cavity of said handle and base of said shank.
 11. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; a pinion gear mounted to said handle; a rack gear mounted to said shank; and a torsion spring connecting to both said pinion gear and said handle; and said pinion gear is engaged to said rack gear.
 12. The tennis racquet of claim 11, wherein said stringed frame head, throat and shank are one integral member.
 13. The tennis racquet of claim 11, wherein said shank and said hollow handle are comprised of complex cross-sections to increase stiffness.
 14. The tennis racquet of claim 11, wherein said handle has a cavity means to accept a portion of said shank.
 15. The tennis racquet of claim 11, wherein said pinion gear is mounted to the shank; said rack gear is mounted to said handle; and said torsion spring connecting to both pinion gear and said shank.
 16. The tennis racquet of claim 1 further including a mechanical stop means between the said shank and the said handle.
 17. The tennis racquet of claim 1, wherein the said spring or flexible means is a torsional spring; and the said torsional spring connecting to the said handle via a pinion gear and a rack gear. 